It is known to produce straight bevel gears, as well as skew bevel gears, face couplings and splined parts, by providing a pair of inclined rotary cutting tools whose rotating cutting blades effectively interlock to simultaneously cut the same tooth space on a workpiece. Examples of this type of machining can be seen, for example, in U.S. Pat. Nos. 2,586,451 to Wildhaber; 2,567,273 and 2,775,921 to Carlsen; 2,947,062 to Spear or in the company brochure “Number 102 Straight Bevel Coniflex® Generator” published by The Gleason Works.
Straight bevel gears may be formed by a non-generating process where the inclined tools are plunged into the workpiece to form a tooth slot with the profile surface of the tooth being of the same form as that of the blade cutting edge. Alternatively, tooth surfaces may be generated wherein the inclined tools are carried on a machine cradle which rolls the tools together with the workpiece to form a generated profile surface on the workpiece. In either instance, the tools may also include cutting edges that are disposed at a slight angle (e.g. 3°) to the plane of cutter rotation. Such an angled cutting edge, in conjunction with the inclination of the tools, removes more material at the ends of a tooth slot thereby resulting in lengthwise curvature of the tooth surface (i.e. lengthwise ease-off) for tooth bearing localization.
It is also known from U.S. Pat. No. 2,342,129 to Elbertz to provide a machine and process for cutting straight bevel gears wherein a single tool is utilized to cut a first portion of a tooth slot followed by a 180° repositioning of the tool or workpiece and subsequently utilizing the tool to cut the remainder of the tooth slot. The path of the tool relative to the workpiece is controlled by a master surface and guides. Lengthwise crowning is not possible with the process of Elbertz given a lack of tool inclination and the cutter would cut shallow at the tooth ends thereby leaving extra metal at the tooth ends. Also with Elbertz, repositioning a work head or tool head by 180° is time consuming and lends itself to machining inaccuracies due to shifting the large mass of a work head or tool head over a considerable travel distance in order to machine the entire tooth slot.